#ifndef MD5_H
#define MD5_H

#include <string>

typedef unsigned char *POINTER;

/**
 * @brief this struct represents a MD5-hash context.
 */
typedef struct 
{
	/** state (ABCD) */
	unsigned long int state[4];   	      

	/** number of bits, modulo 2^64 (lsb first) */
	unsigned long int count[2];

	/** input buffer */
	unsigned char buffer[64];
} HL_MD5_CTX;

// Constants for MD5Transform routine.
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

static unsigned char PADDING[64] = {
  0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/* F, G, H and I are basic MD5 functions. */
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))

/*
 * ROTATE_LEFT rotates x left n bits. 
 * cast to unsigned int to guarantee support for 64Bit System
 */
#define ROTATE_LEFT(x, n) (((x) << (n)) | (( (unsigned int) x) >> (32-(n))))

/*
FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
Rotation is separate from addition to prevent recomputation.
*/
#define FF(a, b, c, d, x, s, ac) { \
 (a) += F ((b), (c), (d)) + (x) + (unsigned long int)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }

#define GG(a, b, c, d, x, s, ac) { \
 (a) += G ((b), (c), (d)) + (x) + (unsigned long int)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define HH(a, b, c, d, x, s, ac) { \
 (a) += H ((b), (c), (d)) + (x) + (unsigned long int)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define II(a, b, c, d, x, s, ac) { \
 (a) += I ((b), (c), (d)) + (x) + (unsigned long int)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }

class MD5
{
	private:
	/**
	 *  @brief 	Basic transformation. Transforms state based on block.
	 *  @param	state	state to transform
	 *  @param	block	block to transform
	 */
	void MD5Transform (unsigned long int state[4], unsigned char block[64])
	{
		unsigned long int a = state[0], b = state[1], c = state[2], d = state[3], x[16];

		Decode (x, block, 64);

		/* Round 1 */
		FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
		FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
		FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
		FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
		FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
		FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
		FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
		FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
		FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
		FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
		FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
		FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
		FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
		FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
		FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
		FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

		/* Round 2 */
		GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
		GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
		GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
		GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
		GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
		GG (d, a, b, c, x[10], S22,  0x2441453); /* 22 */
		GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
		GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
		GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
		GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
		GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */

		GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
		GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
		GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
		GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
		GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

		/* Round 3 */
		HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
		HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
		HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
		HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
		HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
		HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
		HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
		HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
		HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
		HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
		HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
		HH (b, c, d, a, x[ 6], S34,  0x4881d05); /* 44 */
		HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
		HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
		HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
		HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

		/* Round 4 */
		II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
		II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
		II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
		II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
		II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
		II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
		II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
		II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
		II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
		II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
		II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
		II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
		II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
		II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
		II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
		II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

		state[0] += a;
		state[1] += b;
		state[2] += c;
		state[3] += d;

		/* 
		* Zeroize sensitive information.
		*/
		MD5_memset ((POINTER)x, 0, sizeof (x));
	}  

	/**
	 *  @brief 	Encodes input data
	 *  @param	output Encoded data as OUT parameter
	 *  @param	input Input data
	 *  @param	len The length of the input assuming it is a
	 *  		multiple of 4
	 */  
	void Encode (unsigned char *output, unsigned long int *input, unsigned int len)
	{
		unsigned int i, j;

		for (i = 0, j = 0; j < len; i++, j += 4) {
			output[j] = (unsigned char)(input[i] & 0xff);
			output[j+1] = (unsigned char)((input[i] >> 8) & 0xff);
			output[j+2] = (unsigned char)((input[i] >> 16) & 0xff);
			output[j+3] = (unsigned char)((input[i] >> 24) & 0xff);
		}
	}

	/**
	 *  @brief 	Decodes input data into output
	 *  @param	output Decoded data as OUT parameter
	 *  @param	input Input data
	 *  @param	len The length of the input assuming it is a
	 *  		multiple of 4
	 */  
	void Decode (unsigned long int *output, unsigned char *input, unsigned int len)
	{
		unsigned int i, j;

		for (i = 0, j = 0; j < len; i++, j += 4)
			output[i] = ((unsigned long int)input[j]) | 
					(((unsigned long int)input[j+1]) << 8) |
					(((unsigned long int)input[j+2]) << 16) |
					(((unsigned long int)input[j+3]) << 24);
	}

	/**
	 *  @brief 	internal memory management
	 *  @param	output OUT parameter where POINTER is a unsigned
	 *  		char*
	 *  @param	input Data to copy where POINTER is a unsigned char*
	 *  @param	len The length of the data
	 */  
	void MD5_memcpy (POINTER output, POINTER input, unsigned int len)
	{
		/*
		 * TODO-Note: Replace "for loop" with standard memcpy if possible.
		 */
		unsigned int i;

		for (i = 0; i < len; i++)
			output[i] = input[i];
	}

	/**
	 *  @brief 	internal memory management
	 *  @param 	output OUT parameter where POINTER is an unsigned
	 *  		char*
	 *  @param	value Value to fill the memory with
	 *  @param	len The length of the data
	 *  
	 */  
	void MD5_memset (POINTER output,int value,unsigned int len)
	{
		/*
		* TODO-Note: Replace "for loop" with standard memset if possible.
		*/
		unsigned int i;
		for (i = 0; i < len; i++)
			((char *)output)[i] = (char)value;
	}

	//----------------------------------------------------------------------	
	//public member-functions
public:
	/**
	 *  @brief 	Initialization begins an operation,
	 *  		writing a new context
	 *  @param 	context	The HL_MD5_CTX context to initialize
	 */  
	void MD5Init (HL_MD5_CTX *context)
	{
		context->count[0] = context->count[1] = 0;
		context->state[0] = 0x67452301;
		context->state[1] = 0xefcdab89;
		context->state[2] = 0x98badcfe;
		context->state[3] = 0x10325476;
	}

	/**
	 *  @brief 	Block update operation. Continues an md5
	 *  		message-digest operation, processing another
	 *  		message block, and updating the context.
	 *  @param	context The HL_MD5_CTX context to update
	 *  @param	input The data to write into the context
	 *  @param	inputLen The length of the input data
	 */  
	void MD5Update (HL_MD5_CTX *context, unsigned char *input, unsigned int inputLen)
	{
		unsigned int i, index, partLen;

		/* Compute number of bytes mod 64 */
		index = (unsigned int)((context->count[0] >> 3) & 0x3F);

		/* Update number of bits */
		if ( (context->count[0] += ((unsigned long int)inputLen << 3))
			< ((unsigned long int)inputLen << 3))
			context->count[1]++;

		context->count[1] += ((unsigned long int)inputLen >> 29);
		partLen = 64 - index;

		/*
		 * Transform as many times as possible.
		 */
		if (inputLen >= partLen) 
		{
			MD5_memcpy ((POINTER)&context->buffer[index], (POINTER)input, partLen);
			MD5Transform (context->state, context->buffer);

			for (i = partLen; i + 63 < inputLen; i += 64)
			MD5Transform (context->state, &input[i]);

			index = 0;
		}
		else 
			i = 0;

		/* Buffer remaining input */
		MD5_memcpy ((POINTER)&context->buffer[index],
					(POINTER)&input[i],
				inputLen-i);
	}

	/**
	 *  @brief 	Finalization ends the md5 message-digest 
	 *  		operation, writing the the message digest and
	 *  		zeroizing the context.
	 *  @param	digest This is an OUT parameter which contains
	 *  		the created hash after the method returns
	 *  @param	context The context to finalize
	 */  
	void MD5Final (unsigned char digest[16], HL_MD5_CTX *context)
	{
		unsigned char bits[8];
		unsigned int index, padLen;

		/* Save number of bits */
		Encode (bits, context->count, 8);

		/* 
		 * Pad out to 56 mod 64.
		 */
		index = (unsigned int)((context->count[0] >> 3) & 0x3f);
		padLen = (index < 56) ? (56 - index) : (120 - index);
		MD5Update (context, PADDING, padLen);

		/* Append length (before padding) */
		MD5Update (context, bits, 8);

		/* Store state in digest */
		Encode (digest, context->state, 16);

		/*
		 * Zeroize sensitive information.
		 */
		MD5_memset ((POINTER)context, 0, sizeof (*context));
	}

	MD5(){};
};

#endif // MD5_H 